OBJECTIVE The determination of antigen levels and quantitative assays of the biological function of factors VIII and IX in complex mixtures are essential for the success of the projects in this program. The goal of the Coagulation Core is to provide the necessary support and expertise so that these primary objectives are met. In addition to conducting functional assays and immunochemical determinations of antigen levels, the Core will also provide expertise in coagulation and protein chemistry for the further characterization of factor II and IX produced in the various experimental systems used in Project 1-3. These functions of the Core will the availability of appropriate support and expertise for the completion of the aims listed in these projects.